Yes and no. It's in direct relation to how enthused I am on a topic. I can be soft-spoken if I am feeling shy or disinterested, and then I also come off as kind of flat and reserved. If I try to raise my voice then, it has an unnatural quality, lacking warmth, and it will register as angry or annoyed to others. So I don't try to "artificially" raise my voice. However, if I feel enthused and confident, then I can get loud and animated. Then it may be hard for me to lower my volume and speak softly.
I don't have a soft voice, but I have a highpitched, girlish voice. I would say it's childlike, as children have loud squeaky voices, but they are not commanding. Unfortunately, that's what I think I sound like, and so I avoid talking really loudly because I think it gets shrill. If I have to scold loud kids in a class, then I hate how shrill my voice gets.